Method of forming alpha brush shunt connection



1933; c. HOSFIELD 2 METHOD OF FORMING A BRUSH SHUNT CONNECTION FiledJune 24, 1931 2 Sheets-Sheet l INVENTOR:

BY ATTORN EYS Patented Oct. 3, 1933 METHOD OF FORMING A BRUSH smm'r'CONNECTION Lee Conrad Hosfield, Cleveland, Ohio, assignor 1 to NationalCarbon Company, Inc, a'corporation of New York Application June 24,1931. Serial No. 546,611

4 Claims.

This invention relates to brushes for electric machines and especiallyto a method of attaching a shunt toisaid brushes. An object of thisinvention is to secure better electric contact between the shunt cableand the brush body.

' Another object of my invention is to provide additional mechanicalstrength to the rivet holding'that connection to the brush.

. A still further object of my invention is to provide an improvedmethod of making a connection between the shunt cable and the body ofthe brush without the usual tinning operation.

These and other objects of my invention will be evident from thefollowing specification having reference to the annexed drawings inwhich Fig. 1 is an explodedview of the parts of a brush illustrating oneembodiment of my invention.

Fig. 2 is an end view of a spinning tool.

Fig. 3 is a section of the spinning tool taken on the line 33 of Fig. 2.

Fig. 4 is a section showing the start of the spinning operation, thespinning tools being shown in a sectiontaken on the line 4-4 of Fig. 2.

Figs. 5 and 6 are sectional views of one side of the brush showing thespinning operation in an intermediate stage and completed, and

Fig. 7 is an enlarged detail of one end of the spun rivet.

In Fig. 1 I show the parts from which the completed brush with itsshuntconnection are assembled. These comprise a brush body 10 providedwith suitable recesses 11 and 12 for receiving a shunt 13 and washers 14and 15. A hole 16 extends through the brush body to receive a tubularrivet 1'7. The shunt is provided with a loop 18 which is coated withsolder as at 19. The brush body is coated with a suitable conductingmaterial; as copper, at 21. This coating may be applied in any suitablemanner as by spraying.

In assembling the brush and shunt connection, the rivet 1'1 is placedinthe hole 16 and the loop 18 of the shunt is placed around the rivet. Thewashers 14 and 15 are then placed in position. The assembly is thenplaced between a pair of rotating spinning tips 22 and 23 which revolvein opposite directions. I have found speeds of from 900m 1800 R. P. M.suitable, but prefer to use a speed of 1250 R. P. M. The spinning tipsare then forced together, spinning the rivet over as shown in Figs. 5and 6 to form a head of 'the shape shown in detail in Fig. 7. Duringthis spinning operation it is unnecessary to support the brush except tothe extent necessary to prevent its rotation. By using a pair ofspinning tips the heads are formed of substantially equal size and noelaborate means for gaging are necessary.

The spinning tip is shown in detail in Figs. 2 and 3. While I have showna tip having three spinning surfaces it is obvious that other forms maybe used. The shape of the tip is such as to form a head of the shapeshown in Fig. 7. This shape is very advantageous for several reasons.Heretofore, it has been the practice to form a head whose outer surfaceis an arc of a circle of which the brush surface is a chord. This shapedoes not permit the use of as thick a rivet as is possible when therivet head is formed in the shape shown in Fig. 7. My improved shape isfurthermore advantageous since the maximum thickness of metal andmaximum strength is immediately above the outer wall of the rivet. Theshear line coincides with this outer wall and consequently the improvedshape of the spun head produces increased strength of the spun rivetwith consequent greater permanent pressure in the assembled connection.This improved construction obviates the possibility of rupture of thespun heads such as has occurred in the past under severe conditions,especially with respect to vibration and expansion due to heating.Moreover, when it is desired to use a spring washer it is possible touse one of greater resiliency than has heretofore been possible with ariveted construction.

During the spinning operation heat is generated by friction to such anextent as to melt the solder on the loop on the shunt and this soldersweats the loop or eyelet to the copper coating 21 in the counterboreforming good electrical connection. Preferably the loop should also besoldered to the washer. Heretofore, it has been believed necessary totin or solder the entire assembly after the rivet had been spun over. Aflux was used which increased the corrosion of the auxiliary steelparts, such as the washers 14 and 15. Moreover, the heat of the dipsoldering operation annealed and weakened the spun heads of the tubularcopper rivets after they had been hardened by the spinning operation. Inorder to avoid the dip soldering operation it had been proposed topreheat the entire brush and connection and then solder with a solderingiron. This did not, however, avoid the disadvantages of the dipsoldering method.

From the above it will be seen that I have provided a method ofattaching a shunt to a brush which dispenses with the tinning operation;which permits the use of a tubular rivet with thicker walls; which givesa spun-over head of improved shape permitting greater permanentpressures to be used; permitting the use, if dethat a plurality maybe'employed and thatin this case they might be disposed on both sides ofthe brush. In case cables were also disposed on the other side of thebrush they should be beneath the washer 14 so that there would be nopossibility of the spinning tip tearing the cables, r

I claim: 7 V r 1. Method of attaching a shunt to a brush which comprisesproviding ,a solder coated portion of the shunt, depositing conductivematerial around the hole in the brush, placingthe solder coated portionof the shunt adjacent said deposited conductive material and spinningover an end of a rivet disposed in the hole and thereby generatingsufiicient heat to sweat the shunt to said deposited material.

2. Method of attaching a shunt connection to a brush which comprisesapplying solder to the shunt, placing the coated shunt adjacent a rivetand spinning the head of the rivet over with sufiicient force togenerate suflicient heat to melt the solder on the shunt.

3. Method of attaching a shunt to a brush having a hole extendingtherethrough which comprises applying solder to a shunt, applying aconductive coating to' the brush adjacent the hole, placing a rivet insaid hole with the shunt adjacent therethrough and deforming the rivetby spinning with sufficient force to generate sufficient heat to sweatsaid shunt to said conductive coating.

4. Method of attaching a shunt to a brush having a hole therein whichcomprises applying an easily fusible material to the loop in said shunt,depositing conductive metallic material adjacent said hole, placing arivet in said hole with the loopof said shunt adjacent the end of saidrivet and deforming the end of said rivet by spinning with a forcesufiicient to generate enough heat to'sweat said loop to said conductivemetal.

' LEE C. HOSFIELD.

